I first encountered ‘the wrong sort of snow’ in Kate Fox’s Watching the English. I’m not sure that she’s right that once upon a time a train announcement referred to ‘the wrong kind of leaves’ on the track being responsible for the train delay. Her context is ‘The Moan Exception’ – one of the few occasions when British people on a train acknowledge each other’s existence:
if the loudspeaker announcement blames snow for the delay, someone will invariably say: ‘The wrong sort of snow, I suppose?’ I was once waiting for a train at my local station in Oxford when the loudspeaker announced a delay due to ‘a cow on the line outside Banbury’: three people on the platform simultaneously piped up: ‘The wrong sort of cow!’
Wikipedia has a more convincing story of the origin of ‘the wrong type of snow‘:
The wrong type of snow is a phrase coined by the British media in 1991 after severe weather caused disruption to many of British Rail’s services. People who did not realise that there are different kinds of snow saw the reference as nonsensical; in the United Kingdom, the phrase became a byword for euphemistic and lame excuses.
And there are even German references on the Web:
Die offiziellen Erklärungen für die Verspätungen und Ausfälle sorgen auf der Insel immer wieder für Heiterkeit: Mal sind es „Blätter auf den Schienen“ (im Herbst), mal ist es „die falsche Sorte Schnee“ (im Winter), im Rest des Jahres sind es „Weichenprobleme“ oder „fehlende Lokführer“.
LATER NOTE: kalebeul has taken up the topic in a more erudite fashion, as usual.